keith-turner commented on code in PR #2752:
URL: https://github.com/apache/accumulo/pull/2752#discussion_r897416883
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core/src/main/java/org/apache/accumulo/core/util/CompletableFutureUtil.java:
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@@ -49,4 +51,28 @@ public static <T> CompletableFuture<T>
merge(List<CompletableFuture<T>> futures,
return futures.get(0);
}
+ /**
+ * Asynchronously, iterate some function until a given condition is met.
+ */
+ public static <T> CompletableFuture<T>
iterateWhileAsync(Function<T,CompletableFuture<T>> step,
+ Predicate<T> isDone, T init) {
+ // We'd like to use a lambda here, but lambdas don't have
+ // `this`, so we would have to use some clumsy indirection to
+ // achieve self-reference.
+ Function<T,CompletableFuture<T>> go = new Function<>() {
+ @Override
+ public CompletableFuture<T> apply(T x) {
+ if (isDone.test(x)) {
+ return CompletableFuture.completedFuture(x);
+ }
+ // Making the recursive call with thenComposeAsync prevents
+ // stack overflows (but risks deadlock if we run out of
+ // threads).
Review Comment:
Based on the little experiment I did, I don't think this is a potential
problem. In that experiment there were only two threads in the pool and it
iterated 5 times w/o problem.
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